Process for cracking hydrocarbons



May 12, 1925.

W. L. GOMORY PROCESS FOR CRACKING HYDROCARBONS Filed Feb. 24, 1920 Iwufem Patented May 12, 1925.

UNITED STATES 1,537,164 PATENT OFFICE.

WILLIAM L. GOMORY, OF CHICAGO, ILLINOIS, ASSIGNOR TO CLIFFORD M. LEONARD, OF CHICAGO, ILLINOIS.

PROCESS FOR CRACKING HYDROCARBONS.

Application filed February 24, 1920. Serial No. 360,773.

haveinvented certain new and useful Im provements in Processes for Cracking Hydrocarbons, of which the following is a specification.

My invention has for its object to provide a continuous process and apparatus for crackin oil in which a large percentage of the lighter hydrocarbons is obtained with a minimum development of carbon and fixed gases and in which the longevity of the apparatus isincreased and the consumption of fuel reduced to a minimum. With these and other objects in-view, I continuously force a stream of oil or hydrocarbons through a coil heated to a cracking temrature, injecting steam with the oil which as the efl'ect of causing what carbon is developed to assume a porous friable state in WhlCl'l it is readily driven out of the heating coil. The steam further assists in driving the carbon out of the coil. In my process, moreover, the free carbon is at once eliminated, thus increasing the eifectiveness of the apparatus and minimizing the consumption of heat. Other advantages of my invention will appear from the following specification in which I have described a preferred form of apparatus and process; it is to be understood, owever, that the specific disclosure is for the purpose of exemplification only and that the scope of the invention is defined in the following claim in which'I have endeavored todistinguish it from the prior art so far as known to me without however relinquishing or abandoning any portion or feature thereof. i

In the drawings accompanying and forming a part of this application I have shown diagrammatically partly in sectlon and partly in elevation an apparatus embodying and for carrying out my iIlVBIltlOIl. The construction comprises. a furnace 1 which may be of any suitable or approved type, through the heating chamber of which extends a coil of pipe 2' for heating petroleum or other heavy hydrocarbons to be cracked.

Oil is supplied to the coil from a suitable M tank or reservoir through a pipe 3 and is forced through pipe 4 by pump 3 and through to pipe 5 and into the upper end of coil 2. A check-valve 7 in pipe 5 serves to prevent the return of the oil. The oil in the coil of pipe 2 is maintained at a temperature of approximately 1000 Fahrenheit and the oil therein is maintained at a pressure which may be in the neighborhood of 150 pounds, the temperature and pressure being such that 15 to 20 per cent of the oil forced through the coil remains in the liquid phase. In order to assist in the elimination of carbon, as above stated, I introduce steam with the oil, which causes the carbon formed to be in a light, porous condition and which assists in carrying the carbon out of the heating coil, thus greatly increasing the longevity of the apparatus and overcoming one of the greatest difliculties encountered in cracking processes. Fbr this purpose a branch pipe 8 is connected through union 10, check-valve 11 and pipe 9 with a source of steam under pressure.

It will be observed that the oil and steam are introduced at the upper end of the coil 2 and as the evolved gases tend to escape upward through the in-coming current of oil the uncondensable gases are largely re-- absorbed in the oil. From the lower end of the heating coil the mixture of liquid oil, carbon, vapor and fixed gases is conveyed by pipes 6, 14 to the expansion tank 15 in which there is gravity separation, the heavy hydrocarbon containing the free carbon sinking to the bottom of the tank and the uncondensed vapors and gases rising to the top thereof. A gauge 16 indicates the pressure. heavy hydrocarbons containing free carbon are drawn off by pipe 17 into a cooler 18 from which they are conducted to a tank or other storage receptacle by pipe 19'. Thus the carbon developed in the heating coil is at once removed from the system and presents no obstacle to the further cracking operation. The uncondensed portions of the mixture rise through pipe 20 and the heavier portions thereof are condensed in tank 21 and return by pipes 22, 4 and 5 to the heating coil. As this oil contains prac- V tically no free carbon, its return to the heating coil is unobjectionable. The fixed gases and the vapors remaining uncondensed in tank 21 pass over by pipe 21 to From the bottom of the tank the are condensed. From coil 23 the condensed vapors and fixed gases pass through the receiving tank 24 from which the liquid may be drawn off through valve 25. The receiving tank is provided with a pressure gauge 26 and a pressure valve 27, the latter being for the purpose of releasing or carrying away the fixed gases as the pressure rises above the desired point.

The process has been described in connection with the description of the apparatus, but may be briefly stated as follows: Pressure is maintained throu bout the system from the inlet of the heating coil to the receiving tank, slightly diminishing from the former .to the latter but a sufiicient pressure being maintained in the latter to maintain any desired pressure of say approximately 150 pounds in the heating C01l. The temperature of the oil in the heating coil is raised to about 1000 Fahrenheit, the precise temperature and pressure being determined by the fact that about 15 to 20 per cent of the oil is to be maintained in the liquid phase. The heat within the coil results in the splitting up of the heavier hydrocarbons into lighter hydrocarbons with the deposition of carbon, the latter being deposited in porous, friable form because of the introduction of gas for that purpose. At the same time that cracking takes place a considerable volume of noncondensable gas is developed which tends to rise upward in the coil but is thereby brought into contact with, and absorbed by the in-coming stream of oil. The mixed products of the heat treatment are carried over into the expansion tank 15 where they are separted by gravity, the heavier portions containing the fixed carbon settling to the bottom and being drawn off through the cooling tank and then to storage. The portions or components which do not condense in the tank 15 rise through the pipe 20 into tank 21 where the heavier portions thereof are condensed and returned by pipes 22 and 4 to be re-treated, it being noted that this component contains practically no free carbon and therefore introduces no new difiiculty into the treatment. The lighter vapors and fixed gases pass outward through pipe 21 to condenser 23 where the vapors are condensed and flow with the gases into receiving tank 24, Where the liquid is separated from the fixed gas. By separating the free carbon and heavy hydrocarbon and returning only fractions of the oil practically free from the carbon, the life of the coil is increased since practically no carbon is re-introduced thereinto and, furthermore, the consumption of heat is correspondingly reduced.

I claim:

A continuous process for cracking hydrocarbons which consists in mixing steam with the oil to be cracked, continuously forcing the mixture under a pressure about one hundred and fifty pounds through a conduit heated to approximately 1000 F., the temperature and pressure being such as to permit about fifteen to twenty per cent of the hydrocarbons to remain in the liquid phase, passing all the products from said conduit to an enlarged space not directly heated and permitting the heavier, unvaporized hydrocarbons to separate therein without raising their temperature, separately condensing the less volatile and more volatile hydrocarbons and returning the former to the heating conuit.

WILLIAM L. GOMORY. 

